The $1.3 billion project will rebuild road and rail links between Picton and Christchurch.
Abseilers removed rocks and they now monitor slip movement.
"They get to see up close what is happening, what's loose," said site earthworks manager Rob Walker.
"It's pretty high risk for them and for us, but without them we can't continue on.
"All credit to them, you wouldn't see me up there."
Funded by NZ On Air, the interactive documentary's producer said the series aimed to "energise residents to participate in their own recovery".
A young man involved in the highway repair said: "In 20 or 30 years' time, it's still standing, [I can say] I was a part of this, I built this. It feels good."